Noncylindrical stent deployment system for treating vascular bifurcations

ABSTRACT

A device and method for treating pathological narrowing of fluid-carrying conduits of the human body (such as blood vessels) in an area of a bifurcation is disclosed. In particular, a stent system carries a self expandable noncylindrical stent, which is particularly suited for treating a widened portion of a blood vessel immediately proximal to a bifurcation. A stent delivery system is also disclosed, for delivering the stent such that a larger expanded diameter end of the stent faces the bifurcation, and a smaller expanded diameter end of the stent faces proximally in the main vessel.

This is a continuation of U.S. application Ser. No. 10/282,957, filedOct. 28, 2002, now U.S. Pat. No. 7,125,419, which is a continuation ofU.S. application Ser. No. 10/225,484, filed Aug. 20, 2002, which is acontinuation-in-part of U.S. application Ser. No. 09/580,597, filed May30, 2000, the disclosures of which are incorporated by reference intheir entireties.

BACKGROUND

1. Scope of the Invention

The present invention relates to an apparatus permitting the treatmentof bodily conduits, typically blood vessels, in an area of abifurcation, e.g. in an area where a principal conduit separates intotwo secondary conduits. It also relates to equipment for positioningthis apparatus.

2. Description of the Related Art

It is known to treat narrowing of a rectilinear blood vessel by means ofa radially expandable tubular device, commonly referred to as a stent.This stent is introduced in the unexpanded state into the internal lumenof the vessel, in particular by the percutaneous route, as far as thearea of narrowing. Once in place, the stent is expanded in such a way asto support the vessel wall and thus re-establish the appropriate crosssection of the vessel.

Stent devices can be made of a non-elastic material, in which case thestent is expanded by an inflatable balloon on which it is engaged.Alternatively, the stent can be self-expanding, e.g. made of an elasticmaterial. A self-expanding stent typically expands spontaneously whenwithdrawn from a sheath which holds it in a contracted state.

For example, U.S. Pat. Nos. 4,733,065 and 4,806,062 illustrate existingstent devices and corresponding positioning techniques.

A conventional stent is not entirely suitable for the treatment of anarrowing situated in the area of a bifurcation, since its engagementboth in the principal conduit and in one of the secondary conduits cancause immediate or delayed occlusion of the other secondary conduit.

It is known to reinforce a vascular bifurcation by means of a stentcomprising first and second elements, each formed by helical winding ofa metal filament. The first of the two elements has a first part havinga diameter corresponding to the diameter of the principal vessel, and asecond part having a diameter corresponding to the diameter of a firstone of the secondary vessels. The first element is intended to beengaged in the principal vessel and the second element is intended to beengaged in the first secondary vessel. The second element has a diametercorresponding to the diameter of the second secondary vessel. After thefirst element has been put into place, the second element is thencoupled to the first element by engaging one or more of its turns in theturns of the first element.

This equipment permits reinforcement of the bifurcation but appearsunsuitable for treating a vascular narrowing or an occlusive lesion, inview of its structure and of the low possibility of radial expansion ofits two constituent elements.

Moreover, the shape of the first element does not correspond to theshape of a bifurcation, which has a widened transitional zone betweenthe end of the principal vessel and the ends of the secondary vessels.Thus, this equipment does not make it possible to fully support thiswall or to treat a dissection in the area of this wall. Additionally,the separate positioning of these two elements is quite difficult.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, a method of treating a vascular bifurcation of a main vesselinto a first and a second branch vessels. The method comprises the stepsof providing a delivery catheter having a stent thereon, the stenthaving a proximal end and a distal end and being self expandable to aconfiguration in which the proximal end has a smaller diameter than thedistal end. The catheter is positioned such that the stent is at atreatment site within the main vessel, with the distal end adjacent thebifurcation. The stent is deployed in the main vessel such that thedistal end communicates with both the first and the second branchvessels.

In one implementation of the invention, the method additionallycomprises the step of dilating the treatment site prior to thepositioning step. The deploying step may comprise removing a restraintfrom the stent and permitting the stent to self expand. The method mayadditionally comprise the step of deploying a second stent in one of thefirst and second branch vessels.

In one implementation of the invention, the distal end of the stentexpands to a diameter that is at least about 105% of the diameter of theproximal end of the stent. In certain applications, the distal end ofthe stent expands to a diameter that is at least about 110% of thediameter of the proximal end of the stent.

In accordance with another aspect of the present invention, there isprovided a deployment system for treating a bifurcation of a main vesselinto a first and second branch vessels. The deployment system comprisesan elongate flexible body, having a proximal end and a distal end. Atapered stent is carried by the distal end of the body. A releasablerestraint for restraining the stent is also carried by the body. Thedistal end of the stent is larger in diameter than the proximal end ofthe stent in an unconstrained expanded configuration.

The deployment system may additionally comprise a guidewire lumenextending axially through at least a portion of the flexible body. Theguidewire lumen has a proximal access port and a distal access port. Inone implementation, the proximal access port is positioned along theflexible body, spaced distally apart from the proximal end. In anotherimplementation, the proximal access port is positioned at the proximalend of the body.

The releasable restraint may comprise an axially moveable controlelement extending along the length of the flexible body. The releasablerestraint may also comprise a tubular sheath, for restraining the stent.The tubular sheath may be attached to an axially moveable pull wire.

In accordance with a further aspect of the present invention, there isprovided a method of treating a vascular bifurcation of a main vesselinto first and second branch vessels. The method comprises the steps ofdeploying a substantially cylindrical stent in a first branch vesselwhich is distal to the bifurcation, and deploying a tapered stent in themain vessel, proximal to the bifurcation. The tapered stent tapers in adistal direction from a smaller proximal diameter to a larger distaldiameter which faces the bifurcation.

In accordance with another aspect of the present invention, there isprovided a stent deployment catheter. The catheter comprises an elongateflexible tubular body, having a proximal end and a distal end. Anoncylindrical, self expandable stent is carried by the distal end. Ahand piece is provided on the proximal end. A control is provided on thehand piece, for controllably removing a restraint from thenoncylindrical self expandable stent. In one application, the controlhas a first position for indicating a partial deployment of the stent,and a second position indicating complete deployment of the stent.

All of these embodiments are intended to be within the scope of thepresent invention herein disclosed. These and other embodiments of thepresent invention will become readily apparent to those skilled in theart from the following detailed description of the preferred embodimentshaving reference to the attached figures, the invention not beinglimited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus summarized the general nature of the invention, certainpreferred embodiments and modifications thereof will become apparent tothose skilled in the art from the detailed description herein havingreference to the attached figures, of which:

FIG. 1 is a side view of a first embodiment of a stent system shown inan expanded state;

FIG. 2 is a perspective, partial cutaway view of the stent system ofFIG. 1 shown in a state of radial contraction, as disposed on a deliverycatheter;

FIG. 3 is a longitudinal sectional view of a bifurcation treatable bythe stent system of FIG. 1;

FIG. 4 is a section view of the bifurcation of FIG. 3 showing a deliverycatheter positioned therein;

FIG. 5 is a section view of the bifurcation of FIG. 3 showing anembodiment of a stent system shown in a partially contracted state on aportion of a delivery catheter;

FIG. 6 is a section view of the bifurcation of FIG. 3 showing anembodiment of a stent system shown in an expanded and fully deployedstate;

FIG. 7 is a section view of a bifurcation presenting an aneurysm and anembodiment of a stent system shown deployed therein,

FIG. 8 is a side view of a stent system according to a second embodimentshown in an expanded state;

FIG. 9 is a plan view of a delivery catheter usable to deploy a stentsystem having certain features and advantages;

FIG. 9A is an alternative embodiment of a proximal handpiece of thedelivery catheter of FIG. 9;

FIG. 9B is an alternative embodiment of the delivery catheter of FIG. 9;

FIG. 9C is a section view of a portion of the delivery catheter of FIG.9 taken through line 9C-9C and specifically showing an alternative pullwire lumen;

FIG. 9D is a section view of a portion of the delivery catheter of FIG.9 taken through line 9D-9D and specifically showing a retaining band;

FIG. 9E is a detail view of a retraction band retention assembly of thedelivery catheter of FIG. 9;

FIG. 10 is a partial cutaway view of a distal portion of the catheter ofFIG. 9 including a stent system disposed thereon;

FIG. 10A is an alternative embodiment of a distal end assembly of thedelivery catheter of FIG. 9B;

FIG. 10B is a detail view of a distal portion of the outer sheath shownin FIG. 10;

FIG. 10C is a section view taken along the line 10C-10C of FIG. 10;

FIG. 11A is a plan view of a transitional portion of the catheter ofFIG. 9;

FIG. 11B is a cross sectional view of the transitional portion takenalong the line 11B-11B of FIG. 11A;

FIG. 11C is a transverse sectional view of the transitional portiontaken along the line 11C-11C of FIG. 11A;

FIG. 11D is a cross sectional view of the proximal shaft taken along theline 11D-11D of FIG. 11A;

FIG. 12 is a side section view of a distal portion of an embodiment of adelivery catheter having certain features and advantages;

FIG. 13 is a section view of a bifurcation showing an embodiment of adelivery catheter positioned therein;

FIG. 14 is a section view of a bifurcation showing a first stent in apartially deployed state;

FIG. 15 is a section view of a bifurcation showing a first stent in afully deployed state;

FIG. 16 is a section view of a bifurcation showing a second stent in apartially deployed state; and

FIG. 17 is a section view of a bifurcation showing a second stent in afully deployed state.

FIG. 18 is a section view of a bifurcation as in FIG. 17, with a secondbranch stent deployed in the second branch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As described above, the attached Figures illustrate a stent system andcorresponding delivery system for use in treating vessels (e.g.conduits) within the human body at areas of bifurcations. FIG. 3 shows abifurcation 30 in which a main conduit or vessel 32 separates into twosecondary branch conduits or vessels 34. The stent system generallyincludes a pair of dissimilar stents specifically designed for use in anarea of a bifurcation 30. Such dissimilar stents are then disposed on anelongate catheter for insertion into the human body. The dissimilarstents may be self-expanding or manually expandable such as by a balloonabout which the stents may be disposed as will be described in furtherdetail below.

FIG. 1 shows one embodiment of an expandable stent system 10 permittingthe treatment of bodily conduits in the area of a bifurcation such asthat shown. The stent system 10, shown in an expanded state in FIG. 1,generally comprises first 12 and second 14 stent portions which may eachbe divided into two segments, thus creating four successive segments 22,24, 26, 28, of meshwork structure. The first stent 12 is generallyadapted to be disposed in a branch conduit or vessel 34 of abifurcation, while the second stent 14 is generally adapted to bedisposed in a main vessel 32. If desired, the segments may be connectedto one another via one or more bridges of material 18. The stents 12, 14are generally movable between a contracted position and an expandedposition. As will be clear to those skilled in the art, the stents maybe self-expanding or balloon-expandable.

According to the illustrated embodiment, the stents 12, 14 generallycomprise an expandable mesh structure which includes a plurality of meshcells 36. The mesh cells 36 of these segments are in one embodimentelongated in the longitudinal direction of the stents 12, 14 and have ineach case a substantially hexagonal shape in the embodiment shown. Thoseskilled in the art will recognize that the mesh used to form the stentsegments 22, 24, 26, and 28 may comprise a variety of other shapes knownto be suitable for use in stents. For example a suitable stent maycomprise mesh with repeating quadrilateral shapes, octagonal shapes, aseries of curvatures, or any variety of shapes such that the stent isexpandable to substantially hold a vessel or conduit at an enlargedinner diameter.

The first stent 12 may be divided into two segments 22 and 24 which maybe identical to each other and typically have a tubular shape with adiameter which is substantially greater than the diameter of one of thesecondary branch conduits 34. Those skilled in the art will recognizethat the first stent may comprise a variety of shapes such that itfunctions as described herein. The first stent 12 may be expandable to asubstantially cylindrical shape having a constant diameter along itslength. The first stent 12 may comprise a range of lengths depending onthe specific desired location of placement. For example, the length ofthe first stent 12 will typically be between about 1 and about 4centimeters as desired.

The second stent 14 is preferably adapted to be deployed in closeproximity to the first stent 12, and may also be divided into upper 26and lower 28 segments. The lower segment 28 of the second stent 14typically has a tubular cross-sectional shape and has an expandeddiameter which is substantially greater than the diameter of theprincipal conduit 32 (FIG. 3). The upper segment 26 of the second stent14 preferably comprises a larger diameter at its distal (upper) end 38than at its proximal (lower) end 40. In one embodiment the upper segmentof the second stent portion comprises a substantially conical shape. Inan alternative embodiment, the second stent 14 may be tapered radiallyoutward along its entire length in the distal direction. In eitherembodiment however, the expanded diameter of the distal end 38 of thesecond stent 14 is preferably substantially larger than the expandeddiameter of the proximal end 42 of the first stent 12. For example, thedistal end 38 of the second stent 14 may expand to a diameter that is atleast about 105%, and preferably at least about 110%, and in someembodiments as much as 120% or more, of the diameter of the proximal end42 of the first stent 12. The second stent 14 may comprise a range oflengths depending on the specific desired location of placement. Forexample, the second stent 14 will typically be between 1 and 4centimeters as desired.

In its expanded state, as shown in FIG. 1, the upper segment 26 of thesecond stent 14 typically has mesh cells 36 whose width increasesprogressively, compared to that of the meshes of the lower segment 28,on the one hand in the longitudinal sense of the dual stent device 10,in the direction of the distal end 38 of the second stent 14, and, onthe other hand, in the transverse sense of the second stent 14, in thedirection of a generatrix diametrically opposite that located in thecontinuation of the bridge 18. Alternatively stated, the upper segment26 of the second stent 14 preferably comprises a mesh with multiplecellular shapes 36 which may have larger dimensions at a distal end 38of the stent 14 than those at the proximal end 40 such that the secondstent 14 expands to a substantially funnel shape.

In the embodiment shown, this increase in the width of the mesh cells 36results from an increase in the length of the edges 48 of the mesh cells36 disposed longitudinally, as well as an increase in the angle formedbetween two facing edges 48.

This segment 26 thus may have a truncated shape with an axis which isoblique in relation to the longitudinal axis of the first stent 12 whenexpanded. This shape, for example, corresponds to the shape of thebifurcation shown in the area of the widened transitional zone 46 (FIG.3) which separates the end of the principal conduit 32 from the ends ofthe secondary conduits 34. In a preferred embodiment, the second stent14 is placed in close proximity to the first stent 12. For example, thedistal end 38 of the second stent 14 is preferably placed within adistance of about 4 mm of the distal end 42 of the first stent 12, morepreferably this distance is less than about 2 mm, and most preferablythe stents are placed within 1 mm of one another.

In the embodiment shown in FIG. 1, the distance between first and secondstents 12, 14 is held substantially fixed by the provision of a bridge18 between them. Bridges 18 may be provided to join the first and secondstents 12, 14 to one another and/or to join the upper and lower segments22, 24 and 26, 28 of each stent 12 and 14 together. If present, thebridges 18 may connect the adjacent ends of the segments 22, 24 and 26,28 and typically have a small width, so that they can undergo a certainflexion, making it possible to orient these segments in relation to oneanother, in particular the lower segment 24 of the first stent 12 inrelation to the upper segment 26 of the second stent 14.

In addition, in other embodiments, the bridges 18 could be integral withone of the connected segments and separately connected, such as bywelding, to the other connected segment. For example, the bridge 18which connects the first and second stents 12, 14 could be integral withthe upper segment 26 of the second stent 14 and connected to lowersegment 24 of the first segment 26. Alternatively, the bridge 18 couldbe integral with the lower segment 24 of the first stent 12 andconnected to the upper segment 26 of the second stent 14.

In yet other embodiments, bridges 18 could be separate pieces ofmaterials which are separately connected to segments 22, 24, 26, 28 suchas by welding, adhesion, or other bonding method. In all of theseembodiments, the first stent 12 can be made from different pieces ofmaterial than the second stent 14. A tube from which the first stent 12may be made (e.g. by laser cutting techniques) may comprise a smallerdiameter than a tube from which the second stent 14 may be made. Therespective tubes may or may not be made of the same material.Alternatively, the first and second stent may be formed from a singlepiece of material.

When the segments 26 and 28 of the second stent 14 are made from tubesof a smaller diameter than the segments 22 and 24 of the first stent 12,the radial force of the first stent segments 22 and 24 is larger thanthe radial force of the second stent segments 26 and 28, especially atlarger cross sections.

Accordingly, bridges 18 can be made from one of these tubes, and thus beintegral with segments 22 and 24 or segments 26 and 28. Alternatively,the bridges 18 can be separate pieces of material.

In further embodiments, bridges 18 are omitted such that the individualsegments are spaced as desired during installation and use. Theseindividual segments are still delivered and implanted in the same coreand sheath assembly.

The bridges 18 between two consecutive segments could be greater orsmaller in number than six, and they could have a shape other than anomega shape, permitting their multidirectional elasticity, and inparticular a V shape or W shape.

For example, FIG. 8 shows an alternative embodiment of the stent system10 with first 12 and second 14 stents shown in their unconstrained,expanded states. According to this embodiment, each stent 12, 14 may bedivided into two segments 22, 24 and 26, 28 and may include one or moreflexible bridges 18 connecting the first 12 and second stents 14 to oneanother. In this embodiment, the two consecutive segments 22, 24 and 26,28 of the first and second stents 12 and 14, are connected by aplurality (e.g. six) omega-shaped bridges 50. The curved central part 52of these bridges 50 may have a multidirectional elasticity permittingthe appropriate longitudinal orientation of the various segments inrelation to one another. The advantage of these bridges 50 is that theyprovide the stent with longitudinal continuity, which facilitates thepassage of the stent system into a highly curved zone and whicheliminates the need to reduce this curvature, (which may be dangerous inthe cases of arteriosclerosis).

Thus, the stent system 10 of FIG. 8 can comprise several segments 22,24, 26, 28 placed one after the other, in order to ensure supplementarysupport and, if need be, to increase the hold of the stents in thebifurcation 30. The upper segment 26 of the second stent 14 could havean axis coincident with the longitudinal axis of the first stent, andnot oblique in relation to this axis, if such is rendered necessary bythe anatomy of the bifurcation which is to be treated.

Alternatively, the lower segment 24 of the first stent 12 could itselfhave, in the expanded state, a widened shape similar to that of thesecond stent and corresponding to the shape of the widened connectingzone (increasing diameter in the proximal direction) by which, incertain bifurcations, the secondary conduits 34 are connected to thewidened transition zone 46. Thus, the lower segment 24 of the firststent 12, or the entire first stent 12 may have a first diameter at itsdistal end, and a second, larger diameter at its proximal end with alinear or progressive curve (flared) taper in between. According to thisembodiment, this segment 24 would thus have a shape corresponding to theshape of this widened connecting zone, and would ensure perfect supportthereof.

One method of making a self-expanding stent is by appropriate cutting ofa sheet of nickel/titanium alloy (for example, an alloy known by thename NITINOL may appropriately be used) into a basic shape, then rollingthe resulting blank into a tubular form. The blank may be held in acylindrical or frustroconical form by welding the opposing edges of thisblank which come into proximity with each other. The stent(s) may alsobe formed by laser cutting from metal tube stock as is known in the art.Alternatively, a stent may be formed by selectively bending and forminga suitable cylindrical or noncylindrical tubular shape from a single ormultiple wires, or thin strip of a suitable elastic material. Thoseskilled in the art will understand that many methods and materials areavailable for forming stents, only some of which are described herein.

Some Nickel Titanium alloys are malleable at a temperature of the orderof 10° C. but can recover a neutral shape at a temperature substantiallycorresponding to that of the human body. FIG. 2 shows the stent system10 disposed on a delivery catheter in a state of radial contraction. Inone embodiment, a self-expanding stent may be contracted by cooling itsconstituent material of nickel-titanium or other shape-memory alloy to atemperature below its transformation temperature. The stent may later beexpanded by exposing it to a temperature above the transformationtemperature. In the present use, a shape-memory alloy with atransformation temperature at or below normal body temperature may beused. Those skilled in the art will recognize that a self-expandingstent made of a substantially elastic material may also be mechanicallycontracted from its expanded shape by applying a radial compressiveforce. The stent may then be allowed to expand under the influence ofthe material's own elasticity. Nickel titanium and other alloys such assuch as Silver-Cadmium (Ag—Cd), Gold-Cadmium (Au—Cd) and Iron-Platinum(Fe₃—Pt), to name but a few offer desirable superelastic qualitieswithin a specific temperature range.

In one embodiment, the contraction of a stent may cause the mesh celledges 48 to pivot in relation to the transverse edges 49 of the meshcells 36 in such a way that the mesh cells 36 have, in this state ofcontraction, a substantially rectangular shape. Those skilled in the artwill recognize that other materials and methods of manufacturing may beemployed to create a suitable self-expanding stent.

Alternatively, the stents used may be manually expandable by use of aninflatable dilatation balloon with or without perfusion as will bediscussed further below. Many methods of making balloon-expandablestents are known to those skilled in the art. Balloon expandable stentsmay be made of a variety of bio-compatible materials having desirablemechanical properties such as stainless steel and titanium alloys.Balloon-expandable stents preferably have sufficient radial stiffness intheir expanded state that they will hold the vessel wall at the desireddiameter. In the case of a balloon-expandable second stent 14, theballoon on which the second stent 14 is disposed may be specificallyadapted to conform to the desired shape of the second stent 14.Specifically, such a balloon will preferably have a larger diameter at adistal end than at a proximal end.

The present discussion thus provides a pair of dissimilar stentspermitting the treatment of a pathological condition in the area of abifurcation 30. This system has the many advantages indicated above, inparticular those of ensuring a perfect support of the vessel wall and ofbeing relatively simple to position.

For the sake of simplification, the segment which has, in theunconstrained expanded state, a cross section substantially greater thanthe cross section of one of the secondary conduits will be referred tohereinafter as the “secondary segment”, while the segment which has, inthe expanded state, a truncated shape will be referred to hereinafter asthe “truncated segment.”

The secondary segment is intended to be introduced into the secondaryconduit in the contracted state and when expanded will preferably bearagainst the wall of the conduit. This expansion not only makes itpossible to treat a narrowing or a dissection situated in the area ofthe conduit, but also to ensure perfect immobilization of the apparatusin the conduit.

In this position, the truncated segment bears against the wall of theconduit delimiting the widened transitional zone of the bifurcation,which it is able to support fully. A narrowing or a dissection occurringat this site can thus be treated by means of this apparatus, withuniform support of the vascular wall, and thus without risk of this wallbeing damaged.

The two segments may be adapted to orient themselves suitably inrelation to each other upon their expansion.

Advantageously, at least the truncated segment may be covered by amembrane (for example, Dacron® or ePTFE) which gives it impermeabilityin a radial direction. This membrane makes it possible to trap betweenit and the wall of the conduit, the particles which may originate fromthe lesion being treated, such as arteriosclerotic particles or cellularagglomerates, thus avoiding the migration of these particles in thebody. Thus, the apparatus can additionally permit treatment of ananeurysm by guiding the liquid through the bifurcation and therebypreventing stressing of the wall forming the aneurysm.

The segments can be made from tubes of material of a different diameter,as discussed above, with the tube for the truncated segment having alarger diameter than the tube for the secondary segment. The tubes maybe made from the same material. The use of tubes of different diameterscan result in the truncated segment having a larger radial force,especially at larger diameters.

The apparatus can comprise several secondary segments, placed one afterthe other, to ensure supplementary support of the wall of the secondaryconduit and, if need be, to increase the anchoring force of the stent inthe bifurcation. To this same end, the apparatus can comprise, on thatside of the truncated segment directed toward the principal conduit, atleast one radially expandable segment having, in the expanded state, across section which is substantially greater than the cross section ofthe principal conduit.

These various supplementary segments may or may not be connected to eachother and to the two aforementioned segments by means of flexible links,such as those indicated above.

The flexible links can be integral with one of the segments andseparately connected to the other segment, or the flexible links can beseparate pieces of material separately connected to both segments, suchas by welding.

Preferably, the flexible link between two consecutive segments is madeup of one or more bridges of material connecting the two adjacent endsof these two segments. Said bridge or bridges are advantageously made ofthe same material as that forming the segments.

Each segment may have a meshwork structure, the meshes being elongatedin the longitudinal direction of the stent, and each one having asubstantially hexagonal shape; the meshes of the truncated segment mayhave a width which increases progressively in the longitudinal sense ofthe stent, in the direction of the end of this segment having thegreatest cross section in the expanded state.

This increase in the width of the meshes is the result of an increase inthe length of the edges of the meshes disposed longitudinally and/or anincrease in the angle formed between two facing edges of the same mesh.

In addition, the truncated segment can have an axis not coincident withthe longitudinal axis of the secondary segment, but oblique in relationto this axis, in order to be adapted optimally to the anatomy of thebifurcation which is to be treated. In this case, the widths of themeshes of the truncated segment also increase progressively, in thetransverse sense of the stent, in the direction of a generatrixdiametrically opposite that located in the continuation of the bridgeconnecting this segment to the adjacent segment.

The apparatus can be made of a metal with shape memory, which becomesmalleable, without elasticity, at a temperature markedly lower than thatof the human body, in order to permit retraction of the apparatus uponitself, and to allow it to recover its neutral shape at a temperaturesubstantially corresponding to that of the human body. This metal may bea nickel/titanium alloy known by the name NITINOL.

The deployment catheter for positioning the stent or stents comprisesmeans for positioning the stents and means for permitting the expansionof the stents when the latter are in place. These means can comprise acatheter having a removable sheath in which the stent is placed in thecontracted state, when this stent is made of an elastic material, or asupport core comprising an inflatable balloon on which the stent isplaced, when this stent is made of a nonelastic material.

In either case, this equipment comprises, according to the invention,means with which it is possible to identify and access, through the bodyof the patient, the longitudinal location of the truncated segment, sothat the latter can be correctly positioned in the area of the widenedzone of the bifurcation.

In the case where the expansion of this same segment is not uniform inrelation to the axis of the stent, the equipment additionally comprisesmeans with which it is possible to identify, through the body of thepatient, the angular orientation of the stent in relation to thebifurcation to be treated, so that the part of this segment having thegreatest expansion can be placed in a suitable manner in relation to thebifurcation.

Referring to FIG. 9, the stent system is generally deployed using anelongate flexible stent deployment catheter 100. Although primarilydescribed in the context of a multiple stent placement catheter withoutadditional functional capabilities, the stent deployment catheterdescribed herein can readily be modified to incorporate additionalfeatures such as an angioplasty balloon or balloons, with or withoutperfusion conduits, radiation or drug delivery capabilities, or stentsizing features, or any combination of these features, as will bereadily apparent to one of skill in the art in view of the disclosureherein.

The elongate delivery catheter 100 generally includes a proximal endassembly 102, a proximal shaft section 110 including a tubular body 111,a distal shaft section 120 including a distal tubular body 113, and adistal end assembly 107. The proximal end 102 may include a handpiece140, having one or more hemostatic valves and/or access ports 106, suchas for the infusion of drugs, contrast media or inflation media in aballoon expandable stent embodiment, as will be understood by those ofskill in the art. In addition, a proximal guidewire port 172 may beprovided on the handpiece 140 in an over the wire embodiment (see FIG.9A). The handpiece 140 disposed at the proximal end of the catheter 100may also be adapted to control deployment of the stents disposed on thecatheter distal end 104 as will be discussed.

The length of the catheter depends upon the desired application. Forexample, lengths in the area of about 120 cm to about 140 cm are typicalfor use in coronary applications reached from a femoral artery access.Intracranial or lower carotid artery applications may call for adifferent catheter shaft length depending upon the vascular access site,as will be apparent to those of skill in the art.

The catheter 100 preferably has as small an outside diameter as possibleto minimize the overall outside diameter (e.g. crossing profile) of thedelivery catheter, while at the same time providing sufficient columnstrength to permit distal transluminal advancement of the tapered tip122. The catheter 100 also preferably has sufficient column strength toallow an outer, axially moveable sheath 114 to be proximally retractedrelative to the central core 112 in order to expose the stents 118. Thedelivery catheter 100 may be provided in either “over-the-wire” or“rapid exchange” types as will be discussed further below, and as willgenerally be understood by those skilled in the art.

In a catheter intended for peripheral vascular applications, the outersheath 114 will typically have an outside diameter within the range offrom about 0.065 inches to about 0.092 inches. In coronary vascularapplications, the outer sheath 114 may have an outside diameter with therange of from about 0.039 inches to about 0.065. Diameters outside ofthe preferred ranges may also be used, provided that the functionalconsequences of the diameter are acceptable for the intended purpose ofthe catheter. For example, the lower limit of the diameter for anyportion of catheter 100 in a given application will be a function of thenumber of guidewire, pullwire or other functional lumen contained in thecatheter, together with the acceptable minimum flow rate of dilatationfluid, contrast media or drugs to be delivered through the catheter andminimum contracted stent diameter.

The ability of the catheter 100 to transmit torque may also bedesirable, such as to avoid kinking upon rotation, to assist insteering, and in embodiments having an asymmetrical distal end on theproximal stent 14. The catheter 100 may be provided with any of avariety of torque and/or column strength enhancing structures, forexample, axially extending stiffening wires, spiral wrapped supportlayers, or braided or woven reinforcement filaments which may be builtinto or layered on the catheter 100. See, for example, U.S. Pat. No.5,891,114 to Chien, et al., the disclosure of which is incorporated inits entirety herein by reference.

Referring to FIG. 11D, there is illustrated a cross-sectional viewthrough the proximal section 106 of the catheter shaft 100 of FIG. 9.The embodiment shown in FIG. 11D represents a rapid exchange embodiment,and may comprise a single or multiple lumen extrusion or a hypotubeincluding a pull wire lumen 220. In an over-the-wire embodiment, theproximal section 106 additionally comprises a proximal extension of aguidewire lumen 132 and a pull wire lumen 220. The proximal tube 111 mayalso comprise an inflation lumen in a balloon catheter embodiment aswill be understood by those skilled in the art.

At the distal end 107, the catheter is adapted to retain and deploy oneor more stents within a conduit of a human body. With reference to FIGS.10A and 12, the distal end assembly 107 of the delivery catheter 100generally comprises an inner core 112, an axially moveable outer sheath114, and optionally one or more inflatable balloons 116 (FIG. 12). Theinner core 112 is preferably a thin-walled tube at least partiallydesigned to track over a guidewire, such as a standard 0.014 inchguidewire. The outer sheath 114 preferably extends along at least adistal portion 120 of the central core 112 on which the stents 118 arepreferably disposed.

The outer sheath 114 may extend over a substantial length of thecatheter 100, or may comprise a relatively short length, distal to theproximal guidewire access port 172 as will be discussed. In general, theouter sheath 114 is between about 5 and about 25 cm long.

Referring to FIG. 10, the illustrated outer sheath 114 comprises aproximal section 115, a distal section 117 and a transition 119. Theproximal section 115 has an inside diameter which is slightly greaterthan the outside diameter of the tubular body 113. This enables theproximal section 115 to be slideably carried by the tubular body 113.Although the outer sheath 114 may be constructed having a uniformoutside diameter throughout its length, the illustrated outer sheath 114steps up in diameter at a transition 119. The inside diameter of thedistal section 117 of outer sheath 114 is dimensioned to slideablycapture the one or more stents as described elsewhere herein. In astepped diameter embodiment such as that illustrated in FIG. 10, theaxial length of the distal section 117 from the transition 119 to thedistal end is preferably sufficient to cover the stent or stents carriedby the catheter 100. Thus, the distal section 117 in a two stentembodiment is generally at least about 3 cm and often within the rangeof from about 5 cm to about 10 cm in length. The axial length of theproximal section 115 can be varied considerably, depending upon thedesired performance characteristics. For example, proximal section 115may be as short as one or two centimeters, or up to as long as theentire length of the catheter. In the illustrated embodiment, theproximal section 115 is generally within the range of from about 5 cm toabout 15 cm long.

The outer sheath 114 and inner core 112 may be produced in accordancewith any of a variety of known techniques for manufacturing rapidexchange or over the wire catheter bodies, such as by extrusion ofappropriate biocompatible polymeric materials. Known materials for thisapplication include high and medium density polyethylenes,polytetrafluoroethylene, nylons, PEBAX, PEEK, and a variety of otherssuch as those disclosed in U.S. Pat. No. 5,499,973 to Saab, thedisclosure of which is incorporated in its entirety herein by reference.Alternatively, at least a proximal portion or all of the length ofcentral core 112 and/or outer sheath 114 may comprise a metal orpolymeric spring coil, solid walled hypodermic needle tubing, or braidedreinforced wall, as is understood in the catheter and guidewire arts.

The distal portion 117 of outer sheath 114 is positioned concentricallyover the stents 118 in order to hold them in their contracted state. Assuch, the distal portion 117 of the outer sheath 114 is one form of areleasable restraint. The releasable restraint preferably comprisessufficient radial strength that it can resist deformation under theradial outward bias of a self-expanding stent. The distal portion 117 ofthe outer sheath 114 may comprise a variety of structures, including aspring coil, solid walled hypodermic needle tubing, banded, or braidedreinforced wall to add radial strength as well as column strength tothat portion of the outer sheath 114. Alternatively, the releasablerestraint may comprise other elements such as water soluble adhesives orother materials such that once the stents are exposed to the fluidenvironment and/or the temperature of the blood stream, the restraintmaterial will dissolve, thus releasing the self-expandable stents. Awide variety of biomaterials which are absorbable in an aqueousenvironment over different time intervals are known including a varietyof compounds in the polyglycolic acid family, as will be understood bythose of skill in the art. In yet another embodiment, a releasablerestraint may comprise a plurality of longitudinal axial membersdisposed about the circumference of the stents. According to thisembodiment anywhere from one to ten or more axial members may be used toprovide a releasable restraint. The axial members may comprisecylindrical rods, flat or curved bars, or any other shape determined tobe suitable.

In some situations, self expanding stents will tend to embed themselvesin the inner wall of the outer sheath 114 over time. As illustrated inFIGS. 9D and 10A, a plurality of expansion limiting bands 121 may beprovided to surround sections of the stents 12, 14 in order to preventthe stents from becoming embedded in the material of the sheath 114. Thebands 121 may be provided in any of a variety of numbers or positionsdepending upon the stent design. FIG. 10A illustrates the bandspositioned at midpoints of each of the four proximal stent sections 127and each of the five distal stent sections. In an alternativeembodiment, the bands 121 are positioned over the ends of adjacent stentsections. The bands 121 may be made of stainless steel, or any othersuitable metal or relatively non compliant polymer. Of course, manyother structures may also be employed to prevent the self-expandingstents from embedding themselves in the plastic sheath. Such alternativestructures may include a flexible coil, a braided tube, a solid-walledtube, or other restraint structures which will be apparent to thoseskilled in the art in view of the disclosure herein.

The inner surface of the outer sheath 114, and/or the outer surface ofthe central core 112 may be further provided with a lubricious coatingor lining such as Paralene, Teflon, silicone,polyimide-polytetrafluoroethylene composite materials or others known inthe art and suitable depending upon the material of the outer sheath 114and/or central core 112.

As illustrated in FIG. 10B, at least a distal portion of sheath 114 maycomprise a two layer construction having an outer tube 210 and an innertube or coating 212. The exterior surface of the outer tube 210 ispreferably adapted to slide easily within the vessels to be treated,while the inner surface is generally adapted to have a low coefficientof static friction with respect to the stents, thus allowing the sheathto slide smoothly over the stents. The outer tube 210 may, for example,be made of or coated with HDPE or PEBAX, and the inner tube 212 may, forexample, be made of or coated with HDPE, PTFE, or FEP. In an embodimentin which the inner tube is made with a PTFE liner, however, the distalend 214 of the lubricious inner layer or tube 212 is preferably spacedproximally from the distal end 216 of the outer tube 210 by a distancewithin the range of from about 1 mm to about 3 mm. This helps preventthe stent from prematurely jumping distally out of the sheath duringdeployment due to the high lubricity of the PTFE surface.

FIG. 10 illustrates one embodiment of a sheath retraction system. Thesystem illustrated generally includes a sheath pull wire 222, a pullwire slot 224, a sheath retraction band 226, and an outer sheath 114.The sheath retraction band 226 may be a tubular element thermally oradhesively bonded or otherwise secured to a portion of the outer sheath114. In the illustrated embodiment, the retraction band 226 comprises asection of stainless steel tubing having an outside diameter of about0.055 inches, a wall thickness of about 0.0015 inches and an axiallength of 0.060 inches. However, other dimensions may be readilyutilized while still accomplishing the intended function. The sheathretraction band 226 is positioned within the distal portion 117 of theouter sheath 114, just distally of the diameter transition 119. Theretraction band 226 may be connected to the interior surface of theouter sheath 114 by heat fusing a pair of bands 225 to the insidesurface of the outer sheath at each end of the retraction band (see FIG.9E). Alternatively, the retraction band 226 can be attached to the outersheath by using adhesives, epoxies, or by mechanical methods such ascrimping and swaging or a combination of these. In this manner, the pullforce which would be required to proximally dislodge the retraction band226 from the outer sheath 114 is greatly in excess of the proximaltraction which will be applied to the pull wire 222 in clinical use. Thedistal end of the pull wire 222 is preferably welded, soldered, bonded,or otherwise secured to the sheath retraction band 226. The pull wire222 may alternatively be bonded directly to the outer sheath.

The pull wire slot 224 is preferably of sufficient length to allow thesheath 114 to be fully retracted. Thus, the pull wire slot 224 ispreferably at least as long as the distance from the distal end of thestent stop 218 to the distal end of the sheath 114 as shown in FIG. 10A.Slot lengths within the range of from about 1 cm to about 10 cm arepresently contemplated for a two stent deployment system. With thesheath 114 in the distal position as shown, the pull wire slot 224 ispreferably entirely covered by the proximal portion 115 of the sheath114. Alternatively, in an embodiment in which the proximal extension ofsheath 114 extends the entire length of the catheter 100, discussedabove, it can be directly attached to the control 150, in which case apull wire 222 and slot 224 as shown might not be used.

In yet another embodiment illustrated for example in FIGS. 9B and 9C, apull wire lumen 220 may terminate sufficiently proximally from theretraction band 226 that a slot as shown may not be used.

The pull wire 222 may comprise a variety of suitable profiles known tothose skilled in the art, such as round, flat straight, or tapered. Thediameter of a straight round pull wire 222 may be between about 0.008″and about 0.018″ and in one embodiment is about 0.009″. In anotherembodiment, the pull wire 222 has a multiple tapered profile withdiameters of 0.015″, 0.012″, and 0.009″ and a distal flat profile of0.006″×0.012″. The pull wire 222 may be made from any of a variety ofsuitable materials known to those skilled in the art, such as stainlesssteel or nitinol, and may be braided or single strand and may be coatedwith a variety of suitable materials such as Teflon, Paralene, etc. Thewire 222 has sufficient tensile strength to allow the sheath 114 to beretracted proximally relative to the core 112. In some embodiments, thewire 222 may have sufficient column strength to allow the sheath 114 tobe advanced distally relative to the core 112 and stents 12, 14. Forexample, if the distal stent 12 has been partially deployed, and theclinician determines that the stent 12 should be re-positioned, thesheath 114 may be advanced distally relative to the stent 12 therebyre-contracting and capturing that stent on the core.

In general, the tensile strength or compressibility of the pull wire 222may also be varied depending upon the desired mode of action of theouter sheath 114. For example, as an alternative to the embodimentdescribed above, the outer sheath 114 may be distally advanced byaxially distally advancing the pull wire 222, to release the stent 118.In a hybrid embodiment, the outer sheath 114 is split into a proximalportion and a distal portion. A pull wire is connected to the proximalportion, to allow proximal retraction to release the proximal stent. Apush wire is attached to the distal portion, to allow distal advance,thereby releasing the distal stent. These construction details of thecatheter 100 and nature of the wire 222 may be varied to suit the needsof each of these embodiments, as will be apparent to those skilled inthe art in view of the disclosure herein.

The stents 118 are carried on the central support core 112, and arecontracted radially thereon. By virtue of this contraction, the stents118 have a cross section which is smaller than that of the conduits 32and 34, and they can be introduced into these as will be describedbelow. The stents 118 are preferably disposed on a radially inwardlyrecessed distal portion 113 of the central core 112 having a smallerdiameter than the adjacent portions of the core 112. This recess 113 ispreferably adjacent a distal abutment such as a shoulder 124 which maybe in the form of a proximally facing surface on a distal tip 122.Distal tip 122 has an outer diameter smaller than that of the stents 118when the stents are expanded, but greater than the diameter of thestents 118 when they are contracted. This abutment 124 consequentlyprevents distal advancement of the stents 118 from the core 112 when thestents 118 are contracted.

Proximal movement of the stents 118 relative to the core 112 isprevented when the stents are in the radially contracted configurationby a proximal abutment surface such as annular shoulder 125. The distalabutment 124 and proximal abutment 125 may be in the form of annular endfaces formed by the annular recess 113 in the core 112, for receivingthe compressed stents 118. See FIG. 12. In one embodiment, illustratedin FIG. 10A, the proximal abutment 125 is carried by a stent stop 218.Stent stop 218 may be integral with or attached to the central core 112,and has an outside diameter such that it is in sliding contact with theinside surface of outer sheath 114. The compressed stent 14 will thusnot fit between the stop 218 and the outer sheath 114.

The deployment device 100 typically has a soft tapered tip 122 securedto the distal end of inner core 112, and usually has a guidewire exitport 126 as is known in the art. The tapered distal tip 122 facilitatesinsertion and atraumatic navigation of the vasculature for positioningthe stent system 118 in the area of the bifurcation to be treated. Thedistal tip 122 can be made from any of a variety of polymeric materialswell known in the medical device arts, such as polyethylene, nylon,PTFE, and PEBAX. In the embodiment shown in FIG. 10, the distal tip 122comprises an annular recess 230 sized and adapted to allow a distalportion of the outer sheath 114 to reside therein such that thetransition between the tip and the outer sheath comprises a smoothexterior surface.

The distal tip 122 tapers in one embodiment from an outside diameterwhich is substantially the same as the outer diameter of the outersheath 114 at the proximal end 128 of the tip 122 to an outside diameterat its distal end 130 of slightly larger than the outside diameter of aguidewire. The overall length of the distal tip 122 in one embodiment ofthe delivery catheter 100 is about 3 mm to about 12 mm, and in oneembodiment the distal tip is about 8 mm long. The length and rate oftaper of the distal tip 122 can be varied depending upon the desiredtrackability and flexibility characteristics. The tip 122 may taper in alinear, curved or any other manner known to be suitable.

With reference to FIGS. 11B and 12, a distal portion of the central core112 preferably has a longitudinal axial lumen 132 permitting slideableengagement of the core 112 on a guidewire 170. The guidewire lumen 132preferably includes a proximal access port 172 and a distal access port126 through which the guidewire may extend. The proximal access port 172may be located at a point along the length of the catheter 100, as shownin FIGS. 11A and 11B, and discussed below (rapid exchange), or theproximal access port 172 may be located at the proximal end 102 of thecatheter 100 (over the wire). In a rapid exchange embodiment, theproximal access port 172 is generally within about 25 cm of the distalaccess port 126, and preferably is between about 20 cm and about 30 cmof the distal access port 126. The guidewire lumen 132 may benon-concentric with the catheter centerline for a substantial portion ofthe length of the guidewire lumen 132.

FIGS. 11A and 11B illustrate a transition between a proximal shaft tube111 and a distal shaft tube 113 including a proximal guidewire accessport 172 and a guidewire lumen 132. The guidewire lumen 132 may extendthrough a coextrusion, or may be a separate section of tubing which maybe bonded, bound by a shrink wrap tubing, or otherwise held relative tothe proximal shaft tube 111.

In the construction shown in cross-section in FIG. 11B, a proximal shafttube 111 having a pull wire lumen 220 is joined to a distal shaft tube113 having a continuation of pull wire lumen 220 as well as a guidewirelumen 132. In the illustrated embodiment, the proximal shaft tube 111extends distally into the proximal end of connector tubing 230. Amandrel is positioned within each lumen, and shrink tubing 236 is heatedto bond the joint. An opening is subsequently formed in the shrink wrapto produce proximal access port 172 which provides access to theguidewire lumen 132.

In one embodiment, the proximal shaft tube 111 comprises a stainlesssteel hypodermic needle tubing having an outside diameter of about0.025″ and a wall thickness of about 0.003″. The distal end 123 of thehypotube is cut or ground into a tapered configuration. The axial lengthof the tapered zone may be varied widely, depending upon the desiredflexibility characteristics of the catheter 100. In general, the axiallength of the taper is within the range of from about 1 cm to about 5cm, and, in one embodiment, is about 2.5 cm. Tapering the distal end ofthe hypotube at the transition with the distal portion of the catheterprovides a smooth transition of the flexibility characteristics alongthe length of the catheter, from a relatively less flexible proximalsection to a relatively more flexible distal section as will beunderstood by those of skill in the art.

Referring to FIG. 12, a guidewire 170 is illustrated as positionedwithin the guidewire lumen 132. As can be appreciated by those of skillin the art, the diameter of the guidewire 170 is illustrated as slightlysmaller (e.g., by about 0.001-0.003 inches) than the inside diameter ofthe guidewire lumen 132. Avoiding a tight fit between the guidewire 170and inside diameter of guidewire lumen 132 enhances the slideability ofthe catheter over the guidewire 170. In ultra small diameter catheterdesigns, it may be desirable to coat the outside surface of theguidewire 170 and/or the inside walls of the guidewire lumen 132 with alubricous coating to minimize friction as the catheter 100 is axiallymoved with respect to the guidewire 170. A variety of coatings may beutilized, such as Paralene, Teflon, silicone,polyimide-polytetrafluoroethylene composite materials or others known inthe art and suitable depending upon the material of the guidewire 170 orcentral core 112.

As shown in FIG. 12, an inflation lumen 134 may also extend throughoutthe length of the catheter 100 to place a proximal inflation port influid communication with one or more inflatable balloons 116 carried bythe distal end of the catheter.

The inflatable balloon 116, if present, may be positioned beneath one orboth stents, such as stent 14 as illustrated in FIG. 12 or proximally ordistally of the stent, depending upon the desired clinical protocol. Inone embodiment, as illustrated in FIG. 12, the stent may be a selfexpandable stent which is initially released by proximal retraction bythe outer sheath 114 as has been discussed. The balloon 16 is thereafterpositioned in concentrically within the stent, such that it may beinflated without repositioning the catheter to enlarge and/or shape thestent. Post stent deployment dilatation may be desirable either toproperly size and or shape the stent, or to compress material trappedbehind the stent to increase the luminal diameter (e.g. angioplasty). Inan alternate mode of practicing the invention, angioplasty isaccomplished prior to deployment of the stent either by a balloon on thestent deployment catheter 100 or by a separate angioplasty ballooncatheter (or rotational artherectomy, laser or other recanalizationdevice). The stent deployment catheter 100 is thereafter positionedwithin the dilated lesion, and the stent is thereafter deployed. Thus,balloon dilatation can be accomplished using either the deploymentcatheter 100 or separate procedural catheter, and may be accomplishedeither prior to, simultaneously with, or following deployment of one ormore stents at the treatment site.

As seen in FIGS. 9 and 9B, the catheter also includes a handpiece 140 atthe proximal end of the catheter 100. The handpiece 140 is adapted to beengaged by the clinician to navigate and deploy the stent system 118 aswill be described below. The handpiece 140 preferably includes a control150 adapted to control and indicate a degree of deployment of one orboth stents. The control 150 is typically in mechanical communicationwith the sheath 114 such that proximal retraction of the control 150results in proximal retraction of the sheath 114. Those skilled in theart will recognize that distal motion, rotational movement of arotatable wheel, or other motion of various controls 150 mayalternatively be employed to axially move such as distally advance orproximally retract the sheath 114 to expose the stents.

The illustrated control 150 is preferably moveable from a first positionto a second position for partial deployment of the first stent 12, and athird position for complete deployment of the first stent 12. A fourthand a fifth positions are also provided to accomplish partial andcomplete deployment of the second stent 14. The control 150 may includeindicia 160 adapted to indicate the amount of each stent 12 or 14 whichhas been exposed as the sheath 114 is retracted relative to the core112. The indicia 160 may include dents, notches, or other markings tovisually indicate the deployment progress. The control 150 may also oralternatively provide audible and/or tactile feedback using any of avariety of notches or other temporary catches to cause the slider to“click” into positions corresponding to partial and full deployment ofthe stents 12, 14. Alignable points of electrical contact may also beused. Those skilled in the art will recognize that many methods andstructures are available for providing a control 150 as desired.

The catheter 100 may include a plurality of radiopaque markers 250 (seenbest in FIGS. 2, 10, and 10A) impressed on or otherwise bonded to it,containing a radiopaque compound as will be recognized by those skilledin the art. Suitable markers can be produced from a variety ofmaterials, including platinum, gold, barium compounds, andtungsten/rhenium alloy. Some of the markers 250A may have an annularshape and may extend around the entire periphery of the sheath 114. Theannular markers 250A may be situated, in the area of the distal end ofthe first stent 12, the distal end of the second stent 14, and in thearea of the bridge 18 (FIG. 1) or space separating the stents 12, 14. Afourth marker 252 may be situated at substantially the halfway point ofthe generatrix of the lower segment of the second stent 14 situated inthe continuation of the bridge 18 and of the diametrically oppositegeneratrix. FIG. 2 shows a marker 252 with a diamond shape and a smallthickness provided along the outer sheath 114 at a desirable positionfor determining the rotational position of the catheter within thebifurcation. The markers 250, 252, 254 may be impressed on the core 112,on the sheath 114, or directly on the stents 12, 14 such as on thebridge 18, and not on the sheath 114.

With reference to FIGS. 10 and 10A, three markers 253 are shown disposedat a distal end of the second stent 14 and spaced at 120° relative toone another. Three markers 254 are also disposed at a proximal end ofthe first stent 12, and spaced at 120° relative to one another. Eachstent 12, 14 also includes a single marker 250, 210 at its opposite end(e.g. the first stent 12 has a single marker 250 at its distal end, andthe second stent 14 has a single marker 210 at its proximal end). Ofcourse, other marker arrangements may be used as desired by the skilledartisan.

A central marker 252 makes it possible to visualize, with the aid of asuitable radiography apparatus, the position of a bridge 18 separatingthe two stents 12, 14. Thus allowing a specialist to visualize thelocation of the second stent 14 so that it can be correctly positionedin relation to the widened zone 46. The end markers 250A allow aspecialist to ensure that the stents 12, 14 are correctly positioned,respectively, in the main/principal conduit 32 and the secondary/branchconduit 34.

A diamond-shaped marker 252 as shown in FIG. 2 is, for its part, visiblein a plan view or an edge view, depending on whether it is orientedperpendicular or parallel to the radius of the radiography apparatus. Itthus makes it possible to identify the angular orientation of the stents12, 14 in relation to the bifurcation 30, so that the part of the secondstent 14 having the greatest expansion can be placed in an appropriatemanner in relation to the widened transition zone 46.

Methods of positioning and deploying a pair of dissimilar stents in anarea of a bifurcation will now be discussed with reference to FIGS. 3-6and 13-17. Although portions of the following discussion refer todelivery of two dissimilar stent portions, those skilled in the art willrecognize that a larger or smaller number of stents, and/or stentshaving similar expanded configurations may also be used while realizingcertain aspects of the present invention.

A method of delivering a stent system as described above generally andillustrated in FIGS. 13-17 includes locating the bifurcation 30 to betreated, providing a suitable delivery catheter 100, positioning thedistal portion 107 of a delivery catheter with stents 12, 14 disposedthereon in the branch of the bifurcation to be treated, partiallydeploying the first stent 12 in a branch vessel 34, observing andadjusting the position of the first stent 12 if necessary, then fullydeploying the first stent 12. The second stent 14 is partially deployed,and preferably the position is again observed such as by infusingcontrast media through the pull wire lumen 220 under fluoroscopicvisualization. The position of the second stent 14 may be adjusted ifnecessary, and finally the second stent 14 is fully deployed. Methods ofnavigating catheters through blood vessels or other fluid conduitswithin the human body are well known to those skilled in the art, andwill therefore not be discussed herein.

The delivery catheter 100 may be constructed according to any of theembodiments described above such that the stents 12, 14 may beselectively deployed by axially displacing the outer sheath 114 alongthe delivery catheter, thereby selectively exposing the stent system 10.This may be accomplished by holding the sheath 114 fixed relative to thebifurcation, and selectively distally advancing the central core 112.Thus, the present invention contemplates deploying one or more stents bydistally advancing the central core (inner sheath) rather thanproximally retracting the outer sheath as a mode of stent deployment.The stent system may alternatively be deployed by holding the centralcore fixed relative to the bifurcation and selectively proximallyretracting the sheath 114. The catheter may also be adapted to allow thesheath to be advanced distally, thereby re-contracting the partiallydeployed stents on the central core 112 to allow repositioning orremoval.

In order to visualize the position of a partially-deployed stent with asuitable radiographic apparatus, a contrast media may be introducedthrough the catheter to the region of the stent placement. Many suitablecontrast media are known to those skilled in the art. The contrast mediamay be introduced at any stage of the deployment of the stent system 10.For example, a contrast media may be introduced after partiallydeploying the first stent 12, after fully deploying the first stent 12,after partially deploying the second stent 14, or after fully deployingthe second stent 14.

The degree of deployment of the stent system 10 is preferably madeapparent by the indicators on the handpiece 200 as described above. Thehandpiece 200 and outer sheath are preferably adapted such that a motionof a control on the handpiece 200 results in proximal motion of theouter sheath 114 relative to the distal tip 122 and the stents 12, 14.The handpiece 140 and sheath 114 may also be adapted such that thesheath may be advanced distally relative to the stents 12, 14, thuspossibly re-contracting one of the stents 12, 14 on the core 112. Thismay be accomplished by providing a pull wire 222 having a distal end 223attached to a portion of the outer sheath 114, and a proximal endadapted to be attached to the handpiece 200. Alternatively, thehandpiece 200 may be omitted, and the retraction wire 206 may bedirectly operated by the clinician.

In an alternative embodiment, indicated by FIGS. 4-6, the first and/orsecond stent 12, 14 may be deployed in a single motion, thus omittingthe step of re-positioning the stent 12, 14 before fully deploying it.The sheath 114 is then progressively withdrawn, as is shown in FIGS. 5and 6, in order to permit the complete expansion of the stents 12, 14.

In a preferred embodiment, the second stent 14 is placed in closeproximity to the first stent 12. For example, the distal end 38 of thesecond stent 14 may be placed within a distance of about 4 mm of theproximal end 42 of the first stent 12, more preferably this distance isless than about 2 mm, and most preferably the first and second stents12, 14 are placed within 1 mm of one another. Those skilled in the artwill recognize that the relative positioning of the first and secondstents 12, 14 will at least partially depend on the presence or absenceof a bridge 18 as discussed above. The axial flexibility of any bridge18 will also affect the degree of mobility of one of the stents relativeto the other. Thus, a stent system 10 will preferably be chosen to bestsuit the particular bifurcation to be treated.

As mentioned above, the stents 12, 14 may be self-expanding orballoon-expandable (e.g. made of a substantially non-elastic material).Thus the steps of partially deploying the first and/or the second stentmay include introducing an inflation fluid into a balloon on which astent is disposed, or alternatively the stent may be allowed toself-expand. In the case of a balloon-expandable second stent 14, theballoon 116 (FIG. 12A) on which the second stent 14 is disposed may bespecifically adapted to correspond to the particular shape of the secondstent 14. Specifically, such a balloon will preferably have a largerdiameter at a distal end than at a proximal end.

After complete expansion of the stents 12, 14, the distal end of thedelivery catheter 100 including the core 112 and the guidewire 170 maybe withdrawn from the conduits and the vasculature of the patient.Alternatively, additional stents may also be provided on a deliverycatheter, which may also be positioned and deployed in one or bothbranches of the bifurcation. For example, after deploying the secondstent 14 as shown in FIG. 6 or 17, the catheter 100 and guidewire 170may be retracted and re-positioned in the second branch vessel such thata third stent may be positioned and deployed therein.

Referring to FIG. 18, a second branch stent 13 may be deployed in thesecond branch, such that both branch vessels in the bifurcation arefully stented. The second branch stent 13 may be either a selfexpandable or balloon expandable stent such as those well known in theart and disclosed in part elsewhere herein. The second branch stent 13may be deployed before or after the main stent 14 and/or first branchstent 12. In one application of the invention, the main vessel stent 14and first branch stent 12 are positioned as has been described herein. Astent deployment catheter (not illustrated) such as a balloon catheteror self expanding stent deployment catheter is transluminally advancedto the bifurcation, and advanced through the main vessel stent 14. Thesecond branch vessel stent 13 may then be aligned in the second branchvessel, such that it abuts end to end, is spaced apart from, or overlapswith the distal end of the main branch stent 14. The second branchvessel stent 13 may then be deployed, and the deployment catheterremoved.

As will be clear to those skilled in the art, the stent system 10 andstent delivery system 100 described herein is useful in treating anumber of pathological conditions commonly found in vascular systems andother fluid conduit systems of human patients. Treatment with theapparatus can include re-establishing the appropriate diameter of abifurcation in cases of arteriosclerosis or internal cell proliferation,or in rectifying a localized or nonlocalized dissection in the wall ofthe conduit, or in re-creating a bifurcation of normal diameter whileeliminating the aneurysmal pouch in cases of aneurysm.

One or more of the stents deployed in accordance with the presentinvention may be coated with or otherwise carry a drug to be eluted overtime at the bifurcation site. Any of a variety of therapeutically usefulagents may be used, including but not limited to, for example, agentsfor inhibiting restenosis, inhibiting platelet aggregation, orencouraging endothelialization. Some of the suitable agents may includesmooth muscle cell proliferation inhibitors such as rapamycin,angiopeptin, and monoclonal antibodies capable of blocking smooth musclecell proliferation; anti-inflammatory agents such as dexamethasone,prednisolone, corticosterone, budesonide, estrogen, sulfasalazine,acetyl salicylic acid, and mesalamine, lipoxygenase inhibitors; calciumentry blockers such as verapamil, diltiazem and nifedipine;antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel,5-fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine,cisplatin, vinblastine, vincristine, colchicine, epothilones,endostatin, angiostatin, Squalamine, and thymidine kinase inhibitors;L-arginine; antimicrobials such astriclosan, cephalosporins,aminoglycosides, and nitorfurantoin; anesthetic agents such aslidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors suchas lisidomine, molsidomine, NO-protein adducts, NO-polysaccharideadducts, polymeric or oligomeric NO adducts or chemical complexes;anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGDpeptide-containing compound, heparin, antithrombin compounds, plateletreceptor antagonists, anti-thrombin antibodies, anti-platelet receptorantibodies, enoxaparin, hirudin, Warafin sodium, Dicumarol, aspirin,prostaglandin inhibitors, platelet inhibitors and tick antiplateletfactors; interleukins, interferons, and free radical scavengers;vascular cell growth promoters such as growth factors, growth factorreceptor antagonists, transcriptional activators, and translationalpromotors; vascular cell growth inhibitors such as growth factorinhibitors (e.g., PDGF inhibitor—Trapidil), growth factor receptorantagonists, transcriptional repressors, translational repressors,replication inhibitors, inhibitory antibodies, antibodies directedagainst growth factors, bifunctional molecules consisting of a growthfactor and a cytotoxin, bifunctional molecules consisting of an antibodyand a cytotoxin; Tyrosine kinase inhibitors, chymase inhibitors, e.g.,Tranilast, ACE inhibitors, e.g., Enalapril, MMP inhibitors, (e.g.,Ilomastat, Metastat), GP IIb/IIIa inhibitors (e.g., Intergrilin,abciximab), seratonin antagnonist, and 5-HT uptake inhibitors;cholesterol-lowering agents; vasodilating agents; and agents whichinterfere with endogeneus vascoactive mechanisms. Polynucleotidesequences may also function as anti-restenosis agents, such as p15, p16,p18, p19, p21, p27, p53, p57, Rb, nFkB and E2F decoys, thymidine kinase(“TK”) and combinations thereof and other agents useful for interferingwith cell proliferation. The selection of an active agent can be madetaking into account the desired clinical result and the nature of aparticular patient's condition and contraindications.

The bifurcation 30 shown in FIG. 3 has excrescences 35 which create anarrowing in cross section, which impedes the flow of the liquidcirculating in the conduits 32 and 34. In the case of a vascularbifurcation, these excrescences are due, for example, toarteriosclerosis or cellular growth. The stent system described hereinpermits treatment of this bifurcation by re-establishing the appropriatediameter of the conduits 32, 34 and of the widened transition zone 46.

As shown in FIG. 7, the stent system 10 can also be used to treat ananeurysm 242. An aneurysm 242 is defined as a localized, pathological,blood-filled dilatation of a blood vessel caused by a disease orweakening of the vessel's wall. Thus it is desirable to provide a“substitute” vessel wall in an area of an aneurysm. For this purpose,the first or second stent 12, 14 may be at least partially covered by afilm 240 which is substantially impermeable to the liquid circulating inthe conduits 32, 34. Many suitable films are known to those skilled inthe art such as polyester, polytetrafluoroethylene (PTFE), high andmedium density polyethylenes, etc. The film may be sewn onto the stents12, 14, or it may be folded around a stent such that as the stent isexpanded within the vessel 32, the film 240 is trapped and held betweenthe stent and the vessel wall. The stent then guides the liquid throughthe bifurcation 30 and consequently prevents stressing of the wallforming the aneurysm 242.

The stent system described may be adapted as mentioned above to treatany of a number of bifurcations within a human patient. For example,bifurcations of both the left and right coronary arteries, thebifurcation of the circumflex artery, the carotid, femoral, iliac,popliteal, renal or coronary bifurcations. Alternatively this apparatusmay be used for nonvascular bifurcations, such as tracheal or biliarybifurcations, for example between the common bile and cystic ducts, orin the area of the bifurcation of the principal bile tract.

Although certain preferred embodiments and examples have been describedherein, it will be understood by those skilled in the art that thepresent inventive subject matter extends beyond the specificallydisclosed embodiments to other alternative embodiments and/or uses ofthe invention and obvious modifications and equivalents thereof. Thus,it is intended that the scope of the present inventive subject matterherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

1. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel, comprising: positioning a delivery catheter having a stent thereon, wherein the stent comprises an upstream end and a downstream end, such that the stent is at a treatment site within the main vessel with the downstream end adjacent the vascular bifurcation, wherein the stent is self expandable to a configuration having a single central lumen in which the upstream end has a smaller diameter than the downstream end; and deploying the stent in the main vessel by retracting an outer sheath of the delivery catheter, such that the stent self expands to a configuration in which the upstream end has a smaller cross sectional area than the downstream end, and in which the downstream end communicates with both the first branch vessel and the second branch vessel.
 2. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, further comprising deploying a first branch stent into the first branch vessel.
 3. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 2, further comprising deploying a second branch stent into the second branch vessel.
 4. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, wherein the stent comprises a nickel titanium alloy.
 5. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, wherein the delivery catheter further comprises a support core.
 6. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 5, wherein the support core comprises an axial abutment adapted to permit axial immobilization of the stent on the support core.
 7. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 5, wherein the support core comprises a longitudinally extending axial hole adapted to engage a guide wire.
 8. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, further comprising providing an inflatable balloon on the delivery catheter.
 9. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, further comprising providing radiopaque markers on the delivery catheter.
 10. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, further comprising providing radiopaque markers on the outer sheath.
 11. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, further comprising visualizing the location of the stent during deployment.
 12. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, wherein the stent is covered by a film.
 13. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 12, wherein the film comprises polyester.
 14. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, wherein the deploying step further comprises expanding the stent to a shape that corresponds to a transitional zone between the main vessel and the first and second branch vessels.
 15. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 1, wherein the stent is formed by folding and welding a sheet of nickel titanium alloy.
 16. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel, comprising: deploying a branch stent in a first branch vessel that is downstream from the bifurcation; and deploying a tapered stent in the main vessel, upstream from the bifurcation, wherein the tapered stent has a single central lumen and tapers in a downstream direction from a smaller upstream cross section to a larger downstream cross section which faces the bifurcation, and wherein the tapered stent expands to correspond to a shape of the bifurcation.
 17. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, wherein deploying a tapered stent comprises removing a restraint from the tapered stent and permitting the tapered stent to self expand.
 18. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, wherein the tapered stent comprises a nickel titanium alloy.
 19. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, further comprising providing the tapered stent with a delivery catheter.
 20. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 19, wherein the delivery catheter comprises a support core.
 21. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 20, wherein the support core comprises an axial abutment adapted to permit axial immobilization of the tapered stent on the support core.
 22. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 20, wherein the support core comprises a longitudinally extending axial hole adapted to engage a guide wire.
 23. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 19, further comprising providing an inflatable balloon on the delivery catheter.
 24. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 19, further comprising providing a radiopaque marker on the delivery catheter.
 25. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 19, wherein the delivery catheter comprises a sheath.
 26. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 19, further comprising providing a radiopaque markers on the sheath.
 27. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, further comprising visualizing a location of the tapered stent during deployment.
 28. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, wherein the tapered stent is covered by a film.
 29. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 28, wherein the film comprises polyester.
 30. A method of treating a vascular bifurcation of a main vessel into a first branch vessel and a second branch vessel as in claim 16, wherein the tapered stent is formed by folding and welding a sheet of nickel titanium alloy. 